The White House on Wednesday voiced hope the upcoming summit between North Korea's Kim Jong Un and U.S. President Donald Trump will proceed as planned, as Pyongyang threatened to pull out over U.S. pressure for "unilateral nuclear abandonment."

The comments from the North about the meeting, set for June 12 in Singapore, were the first sign of a hiccup after weeks of tentative rapprochement.

"We're still hopeful that the meeting will take place and we'll continue down that path," White House Press Secretary Sarah Sanders told Fox News. "At the same time ... we've been prepared that these might be tough negotiations."

"The president is ready if the meeting takes place. And if it doesn't, we will continue the maximum pressure campaign that has been ongoing."

In an angrily worded statement, the North warned on Wednesday it may back out of the high-level summit if the United States pressures it to give up its nuclear arsenal.

"If the U.S. is trying to drive us into a corner to force our unilateral nuclear abandonment, we will no longer be interested in such dialogue," first vice foreign minister Kim Kye Gwan said in a statement carried by state media.

In that case, he added, Pyongyang would have to "reconsider" its participation at next month's summit in Singapore.

The first vice foreign minister also tore into Trump's National Security Adviser John Bolton for drawing parallels between North Korea and Libya, calling the comparison "absolutely absurd."

"We shed light on the quality of Bolton already in the past, and we do not hide our feeling of repugnance towards him," he said.

Bolton has pushed the idea of a deal with North Korea like that reached with Libya's Muammar Gaddafi, who agreed in 2003 to the elimination of his country's nuclear program and chemical weapons arsenal to gain sanctions relief.

After giving up his atomic program, Gaddafi was killed in 2011 in an uprising backed by NATO bombing.

A plea from China

Washington is pressing for North Korea's complete, verifiable and irreversible denuclearization. But so far, the North has given no public indication of what it is offering, beyond a broad commitment to denuclearization of the "Korean peninsula."

Pyongyang "made clear on several occasions that precondition for denuclearization is to put an end to anti-DPRK hostile policy and nuclear threats and blackmail of the United States," the North Korean minister said.

In the past, Pyongyang has demanded the withdrawal of U.S. troops stationed in the South, and an end to Washington's nuclear umbrella over its ally.

China, North Korea's sole major ally, called for the summit to go ahead.

Timeline: Major nuclear warheads and missiles tested by North Korea

Slideshow by photo services

"The situation on the peninsula has eased up, which is worth cherishing," Chinese foreign ministry spokesman Lu Kang told a regular briefing.

Kim also dismissed offers by U.S. Secretary of State Mike Pompeo for U.S. economic aid if the North denuclearizes.

"We have never had any expectation of U.S. support in carrying out our economic construction and will not at all make such a deal in future," he said.

- Tightrope diplomacy -

The North Korean warning follows a weeks-long charm offensive that has seen Kim hold a historic summit with the South's president and meet twice with Chinese President Xi Jinping.

Pyongyang also raised hopes ahead of the U.S. summit by announcing it will destroy its nuclear testing site next week.

Analysts said Pyongyang appeared to be trying to redefine the terms of the debate.

"It's a diplomatic tactic," Kim Hyun-wook, professor at the Korea National Diplomatic Academy, told AFP, calling it "brinkmanship to change the U.S. position."

"It looks like Kim Jong Un was pushed into accepting U.S. demands for "denuclearization-first" but is now trying to change its position after normalizing North Korea-China relations and securing economic assistance," he added.

"The classic North Korean tightrope diplomacy between the U.S. and China has begun."

U.S. officials have repeatedly credited Washington's "maximum pressure" policy for bringing Pyongyang to the negotiating table.

Joshua Pollack of the Middlebury Institute for International Studies said Pyongyang had been irritated by the "triumphalist tone."

"The North Koreans aren't happy with what they're seeing and hearing," he said. "There is still a yawning gulf between expectations for diplomacy in Pyongyang and Washington, D.C."

Thunderstruck

KCNA also denounced the Max Thunder joint military exercises being held between the U.S. and South Korea as a "rude and wicked provocation," and Seoul said it had received a message canceling planned high-level talks "indefinitely."

The two-week drills started last Friday and involves some 100 aircraft from the two allies, including F-22 stealth fighter jets.

State Department spokeswoman Heather Nauert told reporters it had received "no notification" of a position change by North Korea on next month's meeting.